What is the 30 60 90 rule and the 45 45 90 rule (to do with triangles)

What is the value of n in the equation -1/2(2n+4)+6=-9+4(2n+1)

You buy a veido game for $60 and the sales tax is 8% what is the total cost for the game including the sales tax

Multiply and simplify. (x - 4) (x^2 – 5x – 6) i will mark brainliest if your answer is right. show how you got the answer. if your answer is correct but does not show how you got the answer you will not be marked brainliest.